1. Field of the Invention
The present invention relates to a rear projection screen for use in a rear projection display apparatus which serves to enlarge and project an image on a screen to be observed from the front side, such as a CRT, a liquid crystal panel or a digital mirror device in which the angle of a fine mirror is controlled based on an image signal and the reflected light reflected by the mirror is used. More specifically, it relates to a rear projection screen that can inhibit a deceased contrast caused by external light, which decreased contrast is a problem in rear projection display apparatus of this type.
2. Description of the Related Art
Conventional rear projection screens for use in rear projection display apparatus generally comprise two lens sheets including a Fresnel lens sheet and a horizontal lenticular lens sheet containing a light-diffusing member. However, these rear projection screens invite decreased contrast of the screen because external light from lighting at the ceiling of a room or light reflected from surrounding walls is scattered and reflected at the surface of the screen.
To prevent the reflection of the incident external light and to improve the image contrast, a screen having three sheets including two lenticular lens sheets arranged in a perpendicular direction to each other has been proposed. This type of screens can be found in, for example, Japanese Unexamined Patent Application Publications No 07-5573 and No. 08-101459. In these screens, the ratio of black stripes can be substantially increased and the contrast can be improved by using the lenticular lens sheets arranged in a perpendicular direction to each other.
However, in a screen shown in FIG. 6 including, from a projector side in this order, a Fresnel lens sheet, a vertical lenticular lens sheet and a horizontal lenticular lens sheet, the incident light is reflected at the surface of the vertical lenticular lens and emerges as stray light toward a viewer, thereby causing image deterioration. In a screen shown in FIG. 7 including, from a projector side, a Fresnel lens sheet, a horizontal lenticular lens sheet and a vertical lenticular lens sheet in this order, light from a light source positioned above the viewer, such as lighting, undergoes retroreflection from the lenticular lens on the light source side of the vertical lenticular lens sheet and on the incident-emergent surface of the other lens sheets and appears as stray light, thereby deteriorating the image contrast and decreasing the image quality.